Ved Shaastra always say that one should always speak truth. But sometimes people have difficult situation to follow this. Maybe this story can help them to follow it. This story is from one of the scriptures composed by Sage Vyaas, the Devee Bhaagavat.

Sage Satyavrat had taken the vow of always saying the truth - hence his name as Satyavrat (Vow of Truth). One day he saw a pig came running towards him. He had been struck by an arrow. He stopped, looked about himself and then hid in the bushes nearby. Soon a fierce-looking hunter came following him and started looking for him. When he could not make out to which side the pig had run away, he asked Satyavrat whether he had seen a pig wounded by an arrow. Now Satyavrat was in a flux. If he tells the hunter where the deer is, he will kill him; and if he does not tell him then his vow to speak truth is broken.

So Satyavrat gave an answer which saved the pig, Dharm, and possibly his own life too." What was it?
Very calmly, Sage Satyavrat said, "My eyes have seen but they cannot speak. My mouth can speak but it cannot see. Please leave me alone, O hunter, and go your way." The hunter was so impressed by the courage of this answer that he begged apology and left."

Most importantly, know that if anybody asks a question, one is never obliged to give an answer."
This is a key point to remember: no one is ever required to tell everything, or to answer every question, especially if it might cause harm to the innocent. In other words, non-injury must always supersede truth-telling. This is the golden rule found in many different guises in all religions: "Do no harm". A story from the Puraan confirms this principle. A very respected sage had once blindly adhered to telling the truth, thereby causing the death of hundreds of innocent people. When he died years later, despite his vehement protests that he was a man who had always defended the truth, he was taken to hell. The angel of Death warned him, "By making truth a blind principle, you walked away from the path of compassion, and that is what has led you here."